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Fencer Vulns
high 8.8

CVE-2023-34253 json

Grav vulnerable to Server-side Template Injection (SSTI) via Denylist Bypass

published 2023-06-14 3 y ago modified 2026-06-17 4 mo ago also GHSA-j3v8-v77f-fvgm , EUVD-2023-1830

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

Grav is a flat-file content management system. Prior to version 1.7.42, the denylist introduced in commit 9d6a2d to prevent dangerous functions from being executed via injection of malicious templates was insufficient and could be easily subverted in multiple ways -- (1) using unsafe functions that are not banned, (2) using capitalised callable names, and (3) using fully-qualified names for referencing callables. Consequently, a low privileged attacker with login access to Grav Admin panel and page creation/update permissions is able to inject malicious templates to obtain remote code execution. A patch in version 1.7.42 improves the denylist.

Patch / fix

  • packagist getgrav/grav 1.7.42
  • getgrav grav 1.7.42

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
22 mo ago

Exploit prediction

2.07% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/getgrav/grav/security/advisories/GHSA-j3v8-v77f-fvgm referenced PoC, tagged "exploit" by a source, unverified
  • huntr.dev https://huntr.dev/bounties/3ef640e6-9e25-4ecb-8ec1-64311d63fe66/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
packagist getgrav/grav
<1.7.42
1.7.42

Affected products

  • getgrav grav

Classification

Weakness
  • CWE-184 Incomplete List of Disallowed Inputs
  • CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine
  • CWE-94 Improper Control of Generation of Code

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.